Viscoelastic foam, also known as memory foam, is characterized by its slow recovery after compression and low resiliency. Resilience is an indicator of the surface elasticity or “springiness”. It is measured by dropping a standard steel ball onto the cushion from a given height and measuring the ball rebound percentage. Low resilience viscoelastic foam typically has a ball rebound percentage of less than 20% as compared to 50% to 60% for other flexible polyurethane foam. In addition, viscoelastic foam is able to dampen vibration and absorb shock. Viscoelastic foam allows pressure redistribution by conforming to the shape of the weighted object applying force to it. These properties are desirable in bedding materials, vehicle seating applications, cushioning sports equipment and footwear, ergonomic applications and shock absorbing application.
Polyurethane foams are commonly produced by reacting petroleum-derived polyol and polyisocyanate. However, the recent interest in environment friendly and sustainable products has led to the development and utilization of natural oil-based polyol that are suitable to replace petroleum-based polyol in polyurethane foams manufacturing. WO2006116456 reveals a flexible polyurethane foam produced from a polyisocyanate and natural oil-based polyol.
Introduction of natural oil-based polyol into formulations of viscoelastic foam can affect the foam's resilience and hysteresis properties. Furthermore, formulating and processing range of viscoelastic foams are more restrictive than conventional flexible polyurethane foams. The biggest limitations in using natural oil-based polyol to produce viscoelastic foams is to obtain open cell structure in the foam and avoid shrinkage at high level of foam softness. WO2008063594 relates to a viscoelastic polyurethane foams produced by reacting a polyisocyanate, and a mixture of oligomeric natural oil-based polyol and a petroleum-based derived polyol. However, it is worth mentioning that not all natural oil-based polyol can be used together with petroleum polyol in producing viscoelastic foams.
In this respect, provided herein are viscoelastic polyurethane foams produced by using palm olein-based polyol that exhibit high dissipation energy as calculated based on a hysteresis loop normalized to a same density of 40.8 kg/m3 as the reference commercial viscoelastic foam. This shows an improved dampening property of the viscoelastic foams. In addition, the introduction of palm olein-based polyol improves the load-bearing properties of the viscoelastic foams without affecting the support factors and other mechanical properties.